Threaded locking dowel



United States Patent THREADED LOCKING DOWEL Philip de Anguera, Cincinnati, Ohio, assignor to Graham Tie Dowel Service Company, Columbus, Ohio, a corporation of Ohio Application January 23, 1952, Serial No. 267,774

1 Claim. (Cl. 85-20) The present invention relates to dowels to be driven into timbers and comprises an improved, externally threaded dowel that has a number of uninterrupted spiral ridges extending from end-to-end around its shank, the lead of the spiral ridges on the intermediate portion of the dowel shank being less than the leads of the spiral ridges around the leading and trailing end portions of the dowel shank.

Wood is readily pierced by a spike, nail or dowel driven axially thereinto. Wood however has a good modulus of elasticity, and the body of the wood moved aside by the entrance of these spikes, nails or dowels tends, with considerable force, to return to its original condition, thus gripping their external surfaces and preventing their ready removal from the body of the wood. Upon removal, the body of the wood returns to substantially its original condition because of its good elastic qualities. I have utilized this elastic quality of wood for cooperation with the novel features of my dowel to obtain an improved split resisting, pull up device for timbers which draws the lateral side portions of a timber together as said dowel is being driven laterally therethrough, said dowel being adapted to hold said lateral portions together under considerable compression after it has been driven to its set position within the timber.

It is therefore a particular object of this invention to provide a novel spiral dowel that is self-rotatory when being driven into a timber and which functions as it is being driven to pull together the opposed side portions of the timber and hold them in compression after it has been driven into said timber.

Other objects will be apparent from the following specification and the accompanying drawings which are illustrative of my invention.

In the drawings:

Fig. l is a side elevational view of my dowel.

Fig. 2 is a section taken on line 2--2 of Fig. 1.

Fig. 3 is a section taken on line 33 of Fig. 1.

Fig. 4 is a lateral section taken across one end of a timber provided with two of the dowels shown in Figs. 1-3.

Fig. 5 is an enlarged section taken on line 5--5 of Fig. 4.

Fig. 6 is an enlarged section taken on line 6-6 of Pi 4.

My dowel has a straight shank 1 divided into three sections A, B and C, said shank being formed from endto-end with exteriorly located, spiral ridges 2, 3 and 4, each ridge being continuous throughout the entire length of the dowel shank body. I prefer to employ three spiral ridges, as shown in the drawings, because the most eflective depth of ridge is secured for most kinds of wood timbers without sacrificing the strength of the shank to resist torsional stresses. My dowel may, however, have a number of different cross sectional forms in keeping with the particular characteristics of the timber into which it is to be sunk, it being understood that the harder woods might require a dowel having a square 2,714,831 Patented Aug. 9, 195.5

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shank with four ridges therein, whilst relatively soft woods might require a shank with two or three ridges formed therearound.

As best shown in Figs. 2 and 3 the root diameter of the dowel is the same throughout its length and the spiral ridges 2, 3 and 4 also have corresponding and even depths from end-to-end of the dowel shank. With reference to Fig. 1 it will be noted that the spiral ridges formed on the leading and trailing shank sections A and C respectively have an identical lead which is steep enough to positively rotate the dowel as said sections are being driven into the timber. The degree of inclination of said ridges with respect to the median plane of the shank axis is represented by the included angle a between the section line 22 and the broken line 5, said latter line being inclined at an angle of substantially 45 with said section line. The intermediate portion of the shank is indicated by the portion B which is characterized by the fact that the spiral ridges 2, 3 and 4 have a lead relatively smaller than the lead of the shank portions A and C. The degree of lead for the ridges of section B is indicated by the included angle b between the section line 33 and a broken line 6 which extends along one of the said spiral ridges as it passes through said intermediate section B. The broken line 6 is represented as being inclined at an angle of 30 with the section line 3-3.

The spiral dowel may be formed in the shank by rolling a set of the continuous spiral ridges 2, 3 and 4- in the shank, or said dowel may be constructed by rolling ridges on the shank of identical leads throughout and then twisting the end portion C with respect to the section A in the direction of advance of the spiral ridges, thus deforming the intermediate section B to the point Where the spiral ridge portions thereat have a lead less than the leads of the sections A and C. It is also contemplated that with a a three ridge dowel as shown in the drawing the spiral section C be twisted angulariy approximately out of step with the spiral ridges on section A.

With reference to Fig. 4 it will be noted that the timber 7 is preferably prebored at 8 before driving the spiral dowels thereinto, the diameter of the bore being preferably that of the root diameter of the dowel shank. After formation of the bores 8 the dowels are driven or forced axially into them, the ridges of said section A forcing a spiral track in the wall of the bore to provide a positive rotation for the dowel. As the section B enters and moves through the timber it is rotated by the section A but because the ridges of section B have a smaller lead than the ridges for said section A the ridge portions of section B will rotate through the threaded bore at a greater rate than the ridges on section A. This difference in the leads on the two sections forces the ridges on section B out of the spiral track made in the body of the wood by the ridges on the leading end A of the shank in a direction toward the said leading end, thus drawing the body of the wood through which it passes toward the body of the wood engaged by the ridges of section A as the shank advances through the timber. Because the wood body is resilient the ridges of section B will not shear off the Wood between identical portions of the spiral track formed by section A but will push it back, thus placing the dowel sections A and B in tension and creating an equal and opposite compressive force in the body portion of the wood located between the sections A and B. The spiral portion C is mismatched, or out of step with, the spiral portion A and tends, as it advances into the wood to cut a spiral groove or track in the wood to hold the wood compressed between sections A and B and maintain it in compression for the life of the timber.

it will thus be understood that compression of the lateral side portions of the timber into which my dowel is driven is attained by the resiliency in the Wood whereby the spiral ridges of the center portion B move longitudinally out of the spiral ridges formed in the wood by the sectionA in the direction of the latter section.

This worming action of the ridges of section B is of such force as to set up substantial compressive forces in the wood timber longitudinally of the dowels suflicient set position within a timber is tremendous as the entire 7 lengths of all the ridges cooperate to hold the body of the Wood in the set position of the dowel.

What is claimed is: V

A dowel to be driven into a timber consisting of a straight shank having a plurality of continuous, spiral ridges formed therearound from, end-to-end, and having the same major diameter throughout its length, the

r 4 said spiral ridges having an identical, overall lead at the leading and trailing end portions of the shank and of a degree to permit the said end portions of the dowel to positively rotate the dowel as it is being driven axially into the timber, the said spiral ridges at the leading and trailing end portions being mismatched to form individual spiral tracks in the timber, the intermediate portion of the said ridges having a uniform lead less than the ridge portions on the said ends of the shank, whereby as the'dowel is driven into the timber the timber body portion is compressed by the leading and intermediate portions of the dowel and the trailing portion cooperates withthe leading portion to hold the timber body portion in compression after the dowel is driven to its set position I in the timber.

References Cited in the file of this patent UNITED STATES PATENTS 327,296 McGinIJis Sept. 29, 1885 2,014,892 Graham Sept. 7, 1935 2,095,153 Rosenberg H--. Oct. 5, 1937 2,174,578 Graham Oct. 3, 1939 2,292,557 Wilson Aug. 11, 1942 2,419,555 Fator Apr. 29, 1947 

